this help in material science

1. Thermoplasts
 Plastics which softens up on heating and hardens up
on cooling where the softening and hardening are
totally reversible processes.
 Hence thermoplasts can be recycled.
 They consist of linear molecular chains bonded
together by weak secondary bonds or by inter-winding.
 Cross-linking between molecular chains is absent in
theromplasts.
 E.g.: Acrylics, PVC, Nylons, Perspex glass, etc.

2. Thermoplastics
 Acrylonitrile-butadiene-styrene (ABS):
Characteristics: Outstanding strength and toughness,
resistance to heat distortion; good electrical properties;
flammable and soluble in some organic solvents.
Application: Refrigerator lining, lawn and garden
equipment, toys, highway safety devices.
 Acrylics (poly-methyl-methacrylate) PMMA
Characteristics: Outstanding light transmission and
resistance to weathering; only fair mechanical properties.
Application: Lenses, transparent aircraft enclosures,
drafting equipment, outdoor signs.
Contd…

3.  Fluorocarbons (PTFE or TFE,Teflon)
Characteristics: Chemically inert in almost all
environments, excellent electrical properties; low
coefficient of friction; may be used to 260ooC; relatively
weak and poor cold-flow properties.
Application: Anticorrosive seals, chemical pipes and
valves, bearings, anti adhesive coatings, high temperature
electronic parts.
 Polyamides (nylons)
Characteristics: Good mechanical strength, abrasion
resistance, and toughness; low coefficient of friction;
absorbs water and some other liquids.
Application: Bearings, gears, cams, bushings, handles,
and jacketing for wires and cables.
Contd…

4.  Polycarbonates
Characteristics: Dimensionally stable: low water
absorption; transparent; very good impact resistance
and ductility.
Application: Safety helmets, lenses light globes, base
for photographic film
 Polyethylene
Characteristics: Chemically resistant and electrically
insulating; tough and relatively low coefficient of
friction; low strength and poor resistance to
weathering.
Application: Flexible bottles, toys, tumblers, battery
parts, ice trays, film wrapping materials.
Contd…

5.  Polypropylene
Characteristics: Resistant to heat distortion; excellent
electrical properties and fatigue strength; chemically
inert; relatively inexpensive; poor resistance to UV
light.
Application: Sterilizable bottles, packaging film, TV
cabinets, luggage
 Polystyrene
Characteristics: Excellent electrical properties and
optical clarity; good thermal and dimensional stability;
relatively inexpensive
Application: Wall tile, battery cases, toys, indoor
lighting panels, appliance housings.
Contd…